Abstract

In a conventional anti-lock brake system (ABS) the basic control algorithm is a combination of wheel acceleration/deceleration control and the wheel slip control. This control algorithm depends on the pre-configured threshold values that vary for each braking scenario which requires a large amount of field testing to achieve the best performance. In addition to that, the unpredictable nature of the driving conditions results in limitations not only in tracking the desired slip value within an acceptable range but also in the maximization of the friction force. In this work, a robust ABS algorithm based on Sliding Mode Control (SMC) technique is introduced. It is shown that regardless of uncertainties in the driving conditions the friction force is maximized and the stability of the vehicle is maintained resulting in a shorter brake distance and a better steer ability. For that purpose a self optimization method that calculates the desired slip value and a wheel slip controller to track this slip value are mainly proposed. Similar optimization methods and slip controllers based on SMC can be found in the literature, but these methods are only tested in the Matlab/Simulink environment. In this project the proposed system is analyzed and tested in a vehicle simulator to provide more realistic results. In addition to the optimization method a friction force controller to maintain the friction force balance between the wheels hence maintaining the vehicle stability is also proposed and tested.